TWC: Lambda Control and OBD without Lambda Probe - An Initial Approach

Moos, Ralf; Spörl, Matthias; Hagen, Gunter; Gollwitzer, A.; Wedemann, Marion; Fischerauer, Gerhard

doi:10.4271/2008-01-0916

Cited by 31 publications

(31 citation statements)

References 3 publications

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“…A schematic sketch of the test setup is shown in Figure 1a. Similarly to [12], no attempt has been made at this stage to optimize the coupling of the feeds to the resonator (i.e., to optimize the position and the length of the antennas) because, in contrast to applications, in which the dielectric properties should be measured under process conditions [21], it was the intention to disturb the resonator anyway with the catalyst filling. Therefore, with this system only relative changes in the resonance behavior can be measured.…”

Section: Methodsmentioning

confidence: 99%

“…This microwave-based method has been successfully studied in lab experiments [11] as well as in an engine dynamometer test benches [12]. Even for novel exhaust catalyst systems, like NH3-SCR catalysts, where the amount of stored ammonia needs to be detected [13] or for diesel particulate filters, where the amount of stored soot is an important measurand [14], this microwave-based technique can be applied.…”

Section: Introductionmentioning

confidence: 99%

“…Further details on the microwave cavity perturbation method applied in the automotive exhaust can be found in [15,18,19]. Prior investigations with this method on the state observation of three-way catalysts with the size of ∅ 4.66″ × 6″ (∅ 11.84 cm × 15.24 cm; full size as it is installed in the exhaust pipe) [11,12,20] and ∅ 1″ × 3″ (∅ 2.54 cm × 7.62 cm; typical lab sample) [6,8] have shown that there is a good correlation between the resonance parameter "resonance frequency" and the catalysts' oxidation states.…”

Section: Introductionmentioning

confidence: 99%

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In operando Detection of Three-Way Catalyst Aging by a Microwave-Based Method: Initial Studies

2015

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Initial studies on aging detection of three way catalysts with a microwave cavity perturbation method were conducted. Two physico-chemical effects correlate with the aging state. At high temperatures, the resonance frequencies for oxidized catalysts (λ = 1.02) are not influenced by aging, but are significantly affected by aging in the reduced case (λ = 0.98). The catalyst aging state can therefore potentially be inferred from the resonance frequency differences between reduced and oxidized states or from the resonance frequency amplitudes during lambda oscillations. Secondly, adsorbed water at low temperatures strongly affects the resonance frequencies. Light-off experiment studies showed that the resonance frequency depends on the aging state at temperatures below the oxygen storage light-off. These differences were attributed to different water sorption capabilities of differently aged samples due to a surface area decrease with proceeding aging. In addition to the aging state, the water content in the feed gas and the temperature affect the amount of adsorbed water, leading to different integral electrical material properties of the catalyst and changing the resonance properties of the catalyst-filled canning. The classical aging-related properties of the catalyst (oxygen storage capacity, oxygen storage light-off, surface area), agreed very well with data obtained by the microwave-based method. OPEN ACCESSAppl. Sci. 2015, 5 175

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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In operando Detection of Three-Way Catalyst Aging by a Microwave-Based Method: Initial Studies

2015

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“…Instead, they are intended to detect the status of full-sized exhaust gas aftertreatment devices during operation on the road. Typical applications are the determination of the oxygen loading of three-way catalytic converters (Moos et al, 2008Beulertz et al, 2013;Reiß et al, 2011a), or the soot loading (Sappok et al, 2010;Feulner et al, 2013) or ash loading (Kulkarni et al, 2013) of fullsized diesel particulate filters. The storage degree of NO in lean NO x traps (Fremerey et al, 2011;Moos et al, 2009) and the NH 3 loading on SCR catalyst devices have also been successfully monitored (Reiß et al, 2011b;Rauch et al, 2014Rauch et al, , 2015 using the cavity perturbation method.…”

Section: Introductionmentioning

confidence: 99%

Ammonia storage studies on H-ZSM-5 zeolites by microwave cavity perturbation: correlation of dielectric properties with ammonia storage

Dietrich

Rauch

Simon

et al. 2015

J. Sens. Sens. Syst.

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Abstract.To meet today's emission standards, the ammonia-based selective catalytic reduction (SCR) has become the major NO x control strategy for light and heavy diesel engines. Before NO x reduction can proceed, adsorption of ammonia on the acidic sites of the catalyst is necessary. For improvements in efficiency and control of the exhaust gas aftertreatment, a better understanding of the ammonia storage on the acidic sites of zeolite-based SCR catalysts is needed. Thereby, the correlation of dielectric properties of the catalyst material itself with the ammonia storage is a promising approach. Recently, a laboratory setup using microwave cavity perturbation to measure the dielectric properties of catalyst material has been described. This study shows the first experimental data on zeolite-based SCR materials in their H-form. The SCR powder samples are monitored by microwave cavity perturbation while storing and depleting ammonia, both with and without admixed NO x at different temperatures. Its complex dielectric permittivity is found to correlate closely with the stored mass of ammonia. The influence of the temperature and the Si / Al ratio of the zeolite to the ammonia storage behavior are also examined. These measurements disclose different temperature dependencies and differing sensitivities to ammonia storage for both real and imaginary parts of the complex permittivity. The apparent constant sensitivity of the real part can be related to the polarity of the adsorbed ammonia molecules, whereas the imaginary part depends on the Si / Al ratio and is related to the conductivity mechanisms of the zeolite material by proton hopping. It provides information about the zeolite structure and the number of (and the distance between) acidic storage sites, in addition to the stored ammonia mass.

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“…Since the electronic conductivity of ceria-zirconia solutions depends on the equilibrium oxygen partial pressure (Boaro et al, 2002), pO 2 , which is a measure of the oxygen loading degree (Mo¨ller et al, 2009), a direct catalyst state control determining the overall oxygen loading may be possible (Moos et al, 2008b).…”

Section: Application To Three-way Catalystsmentioning

confidence: 99%

Automotive Catalyst State Diagnosis Using Microwaves

Moos

Fischerauer

2014

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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-The state of catalysts plays a key role in automotive exhaust gas aftertreatment. The soot or ash loading of Diesel particulate filters, the oxygen loading degree in three-way catalysts, the amount of stored ammonia in SCR catalysts, or the NO x loading degree in NO x storage catalysts are important parameters that are today determined indirectly and in a model-based manner with gas sensors installed upstream and/or downstream of the catalysts. This contribution gives an overview on a novel approach to determine the catalyst state directly by a microwave-based technique. The method exploits the fact that the catalyst housing acts as a microwave cavity resonator. As "sensing" elements, one or two simple antennas are mounted inside the catalyst canning. The electrical properties of the catalyst device (ceramic honeycomb plus coating and storage material) can be measured. Preferably, the resonance characteristics, e.g., the resonance frequencies, of selected cavity modes are observed. The information on the catalyst interior obtained in such a contactless manner is very well correlated with the catalyst state as will be demonstrated for different exhaust gas aftertreatment systems.Re´sume´-Diagnostic de l'e´tat de catalyseurs d'automobiles a`l'aide de micro-ondes -L'e´tat des catalyseurs joue un roˆle essentiel dans le post-traitement des gaz d'e´chappement automobiles. Le chargement en suie ou en cendres des filtres Diesel a`particules, la teneur en oxyge`ne dans les catalyseurs trois voies, la quantite´d'ammoniac stocke´e dans les catalyseurs SCR ou le niveau de chargement en NO x dans les catalyseurs de stockage de NO x sont des parame`tres importants de´termine´s aujourd'hui de manie`re indirecte et sur la base de mode`les avec des capteurs de gaz se trouvant en amont et/ou en aval des catalyseurs. Cette contribution pre´sente une nouvelle approche permettant de de´terminer l'e´tat du catalyseur, directement en utilisant une technique a`micro-ondes. La me´thode exploite le fait que le boıˆtier du catalyseur agit comme cavite´re´sonnante de micro-ondes. En tant qu'e´le´ments de de´tection, une ou deux antennes simples sont installe´es a`l'inte´rieur du conditionnement du catalyseur. Les proprie´te´s e´lectriques du dispositif catalytique (nid d'abeille en ce´ramique plus reveˆtement et mate´riau de stockage) peuvent eˆtre mesure´es. De pre´fe´rence, les caracte´ristiques de re´sonnance, par exemple les fre´quences de re´sonnance, des modes de cavite´se´lectionne´s, sont observe´es. Les donne´es obtenues de cette manie`re sans contact, sont tre`s bien corre´le´es avec l'e´tat du catalyseur, tel que cela sera de´montre´pour diffe´rents syste`mes de post-traitement des gaz d'e´chappement.

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TWC: Lambda Control and OBD without Lambda Probe - An Initial Approach

Cited by 31 publications

References 3 publications

In operando Detection of Three-Way Catalyst Aging by a Microwave-Based Method: Initial Studies

In operando Detection of Three-Way Catalyst Aging by a Microwave-Based Method: Initial Studies

Ammonia storage studies on H-ZSM-5 zeolites by microwave cavity perturbation: correlation of dielectric properties with ammonia storage

Automotive Catalyst State Diagnosis Using Microwaves

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